That's one thing I have to say about the tailor I use. He knows what he's doing when it comes to sleeve lengths.
That said, I think that salespeople in menswear shops have a lot to answer for. When I bought my first suit a few years back, the SA measured me up, which I thought was fine. It turns out that for years, my suit sleeves were too long, as were the legs on my trousers. Perhaps he'd been conditioned into being a little generous with these measurements through years of browbeating by the wives and mothers of his customers?